User blog:Fuse809/Antibodies and disease
It's interesting to think how many diseases and other medical ailments antibodies play a pivotal role in. Relevant background information Antibodies'''Click this link to see some further information on this Wiki are '''Y-shaped proteins produced by the plasma cells of the immune system. They comprise two major domains: Fab and Fc. Fab are the two diagonal fragments of the Y (the part that looks like a 'v') whereas Fc is the vertical I-like component. Fab fragments are the parts of the antibody that bind to antigens. Antigens are the substances, usually proteins, that initially stimulate B cells to develop into (a process called B cell "activation") plasma cells which in turn secrete the antibodies. Every antibody produced by these plasma cells are designed so that their Fab regions bind to the antigen that triggered the initial B cell activation. B cell activation usually requires some input by another subset of immune cells called helper T cells (TH cells), as the B cells ingest the antigen and break it down to make it possible for it to be fused to MHC class II molecules which are then sent to the cell's surface. These complexes of antigen fragments bound to MHC class II molecules are recognizable by helper T cells and their surface receptors, and once recognized they activate the TH cells and the TH cells then secrete several compounds that get the B cell ready to produce antibodies. Antibodies are also called immunoglobulins (Igs) and there are several distinct types (or isotypes) of them: IgA, IgD, IgE, IgG and IgM. They are distinguished by differing specific structural features and roles in the body. Antibodies and disease Antibodies play a critical role in most hypersensitivity reactions (HSRs; immune-mediated tissue injury) including: type I HSRs (allergies), type II HSRs (their definition is that they are predominantly due to the direct effects of IgG and/or IgM antibodies) and type III HSRs (which are defined as being due to immune complex deposition. Immune complexes are the overall structures formed by antigens binding to antibodies). Type I HSRs include allergies like hay fever, hives, anaphylaxis, etc. and asthma. They involve environmental antigens (i.e., antigens found in the person's environment, like pollen or those in foods like nuts or dairy) that are called allergens and they specifically stimulate IgE secretion as opposed to other immunoglobulin isotypes. IgE then stimulates another class of immune cell called mast cells to secrete histamine and other immune signalling molecules. Histamine mediates immediate reactions like swelling (including potentially in the airways as in anaphylaxis which can be life-threatening if severe enough), itching, lowering blood pressure, mucus secretion (e.g., runny nose in hay fever), etc. '' '' Type II HSRs include myasthenia gravis (a condition characterized by muscle weakness due to the antibodies blocking the receptors in the neuromuscular junction which is where nerves communicate with one's muscles; they are required for all voluntary muscle movement, like moving your hands or arms, etc.), Goodpasture syndrome, Wegener granulomatosis, autoimmune haemolytic anaemia, pernicious anaemia, Graves disease, rheumatic fever, etc. Type III HSRs include systemic lupus erythematosus (SLE) and poststreptococcal glomerulonephritis and are caused by the deposition of immune complexes in the tissues, especially in the glomeruli of the kidneys. These immune complexes trigger inflammatory responses Amyloidosis Two types of amyloidosis, AH and AL amyloidosis, are due to the deposition of misfolded immunoglobulin heavy/light chain proteins, respectively, in the tissues, leading to their dysfunction and injury. Notes